The present invention relates generally to a fluid flow control device for use with an evacuated blood collection container in the collection of blood from a patient, and more particularly, concerns a fluid flow control device for such use which is operable to control the vacuum pressure applied through a blood collecting needle cannula.
In the procedure of collecting blood from a patient, the collection operator generally has no effective control over the flow of blood from the patient into the evacuated blood collection container. This is due to the fact that the blood collection devices generally known and used in today's market have no provision to provide such control. Control of blood flow becomes particularly important in those instances when veins collapse or occlude the needle.
These situations arise more frequently nowadays since most blood is collected from a patient with the use of an evacuated blood collection container. If a patient should have a weak vein, the high initial vacuum in the blood collection container is believed to suck the vein wall against the bevel of the needle or collapse the vein itself, whereby blood flow ceases. With no mechanism available to shut off the vacuum, the operator generally resorts to some makeshift means of dealing with the situation, ranging from rotating the needle while in the vein to removing the evacuated blood container altogether. Of course, the needle rotation could be very traumatic to the patient, while removal of the needle altogether will require a second attempt to make the blood collection. Accordingly, there is a need for valving or throttling the evacuated blood collection container so as to have an effective control of the vacuum applied to the patient's vein.
One such vacuum blood drawing device is disclosed in U.S. Pat. No. 3,491,748. In that patent, the device allows the vein to refill by blocking the vacuum from the evacuated blood container by pressing a flexible tube against a control surface, the pressure being applied by the thumb of the operator. The overall construction of this patented device is somewhat complicated and could add expense to its manufacture. In addition, reliance upon the projecting pressure surface in conjunction with the flexible tube for flow control raises the possibilities of misalignment and perhaps unnecessary bulk to this type of device. Therefore, there is still a need for further improvements in this type of device which controls the vacuum pressure from an evacuated blood collection container during the blood collecting procedure.